Automotive vehicle steering system having an electric motor powered linear actuator shaft for turning a steered wheel

Abstract

An automotive vehicle steering system has an actuator ( 12 ) for steering a wheel ( 10 ). A shaft ( 28 ) passes axially through the interior of a housing ( 14 ) of the actuator and through a rotor tube ( 56 ) journaled for rotation within the housing. On the exterior of the housing one end of the shaft is coupled to the wheel. An electric motor ( 52 ) within the interior of the housing rotates the rotor tube when the wheel is steered by a steering wheel. An internal screw thread ( 68 ) on the rotor tube and an external screw thread ( 70 ) on the shaft are operatively coupled by a set ( 74 ) of transmission rollers ( 76 ) to provide for bi-directional transmission of motion between the rotor tube and the shaft such that rotation of the rotor tube causes the shaft to move axially of the housing to steer the vehicle wheel and axial motion of the shaft due to wheel recovery from a turn rotates the rotor tube.

1. An automotive vehicle steering system comprising:
 a steered wheel;  
 and an actuator for turning the steered wheel about a turning axis to steer the wheel;  
 the actuator comprising a housing that comprises an interior enclosed by an axially extending side wall having opposite axial ends;  
 a shaft that has a longitudinal axis coaxial with the housing side wall, an interior axial end disposed within the interior of the housing and an exterior axial end that is exterior to the interior of the housing;  
 an electric motor comprising a rotor that is disposed within the interior of the housing for rotation about an axis that is coaxial with the shaft axis, the rotor comprising a cylindrical rotor tube comprising an open axial end through which the shaft coaxially passes, and which is rotatable about the coaxis of the shaft and rotor, the motor further comprising a stator for operating the rotor to rotate the rotor tube;  
 an internal screw thread on the rotor tube;  
 an external screw thread on the shaft;  
 a set of transmission rollers operatively coupling the internal screw thread and the external screw thread to provide for bi-directional transmission of motion between the rotor tube and the shaft such that rotation of the rotor tube causes the shaft to move axially of the housing and axial motion of the shaft causes rotation of the rotor tube; and  
 a coupling that couples the exterior axial end of the shaft to the wheel;  
 wherein the transmission rollers comprise identical screw threads meshing with the internal and external screw threads, and in which the internal, external, and transmission roller screw threads all have the same number of threads per unit of axial length.  
 
   
   
     2. An automotive vehicle steering system as set forth in  claim 1  including support rings disposed on the shaft at opposite ends of the transmission rollers for locating the transmission rollers spaced circumferentially apart about the coaxis and journaling the transmission rollers, and in which the transmission rollers include gear teeth meshed with pinions on the shaft to cause the transmission rollers to turn about their own axes as they transmit motion between the internal and external screw threads. 
   
   
     3. An automotive vehicle steering system as set forth in  claim 1  including a steering wheel that is turned to steer the wheel via a transmitter that delivers electric signals to an electric controller that operates the electric motor to cause the shaft to translate in correlation with turning of the steering wheel to thereby steer the wheel. 
   
   
     4. An automotive vehicle steering system comprising:
 a steered wheel;  
 and an actuator for turning the steered wheel about a turning axis to steer the wheel;  
 the actuator comprising a housing that comprises an interior enclosed by an axially extending side wall having opposite axial ends;  
 a shaft that has a longitudinal axis coaxial with the housing side wall, an interior axial end disposed within the interior of the housing and an exterior axial end that is exterior to the interior of the housing;  
 an electric motor comprising a rotor that is disposed within the interior of the housing for rotation about an axis that is coaxial with the shaft axis, the rotor comprising a cylindrical rotor tube comprising an open axial end through which the shaft coaxially passes, and which is rotatable about the coaxis of the shaft and rotor, the motor further comprising a stator for operating the rotor to rotate the rotor tube;  
 an internal formation on the rotor tube;  
 an external formation on the shaft;  
 a set of elements operatively coupling the internal formation and the external formation to provide for bi-directional transmission of motion between the rotor tube and the shaft such that rotation of the rotor tube causes the shaft to move axially of the housing and axial motion of the shaft causes rotation of the rotor tube;  
 individual elements of the set being disposed circumferentially spaced apart about the coaxis of the shaft and rotor tube with the elements meshing with both the internal formation and the external formation and with the elements planetating about the coaxis as they transmit motion between the two formations; and  
 a coupling that couples the exterior end of the shaft to the wheel;  
 wherein the elements comprise transmission rollers, the internal formation comprises a helical internal screw thread, the external formation comprises a helical external screw thread, and the transmission rollers comprise respective screw threads, and  
 the helical internal screw thread, the helical external screw thread, and the transmission roller screw threads all have the same number of threads per unit of axial length.  
 
   
   
     5. An automotive vehicle steering system as set forth in  claim 4  including support rings disposed on the shaft at opposite ends of the transmission rollers for locating the transmission rollers spaced circumferentially apart about the coaxis and journaling the transmission rollers, and in which the transmission rollers include pinions meshed with a pinion on the shaft to cause the transmission rollers to planetate. 
   
   
     6. An automotive vehicle steering system as set forth in  claim 4  including a steering wheel that is turned to steer the wheels via a transmitter that delivers electric signals to an electric controller that operates the electric motor to cause the shaft to translate in correlation with turning of the steering wheel to thereby steer the vehicle.